import string


def radix_convert(number, radix):
    s = []
    while number > 0:
        s.append(number % radix)
        number = number // radix
    return s[::-1]

N = int(input())
S = ''.join([string.ascii_uppercase[e - 1] for e in radix_convert(N, 26)])[:-1]
print(S + string.ascii_uppercase[N % 26])